In recent years, input apparatuses having touch sensors such as touch panels, touch switches or the like are popularly used as input apparatuses such as operation units, switches and the like for receiving input operations by a user in mobile terminals such as mobile phones, gaming machines, information equipments such as calculator, ticket vending machines, home electric appliances such as microwaves, TV sets, lighting equipments, industrial equipments (FA equipments) and the like.
There are known a variety of types of those touch sensors, such as a resistive film type, a capacitive type, an optical type and the like. However, touch sensors of these types receive a touch input by a finger or a stylus pen and, unlike push-button switches, the touch sensors themselves are not physically displaced even when being touched.
Since the touch sensors are not physically displaced when touched, an operator cannot obtain feedback to an input even when the touch input is received. As a result, the operator is likely to input erroneously by touching the same spot multiple times, which may be stressful for the operator.
As methods to prevent such repetitious inputs, there are known methods of visually or auditory confirming the input operations by, for example, generating sounds or by changing a display state, such as colors of input objects such as input buttons and the like graphically depicted on a display unit, according to an input position upon reception of the touch input.
However, such auditory feedback may be difficult to be confirmed in a noisy environment and is not applicable when the equipment being used is in a silent mode. In addition, in using such visual feedback, when the operator is inputting by the finger, if the input object displayed on the display unit is small, the operator may not be able to confirm the change in the display state, as a view of the input object is blocked by a finger.
There is also suggested a feedback method relying on neither the auditory- nor visual sensation but instead generating a tactile sensation at operator's fingertip by vibrating the touch sensor when the touch sensor receives an input (for example, see Patent Documents 1, 2).
As a method to provide a more detailed tactile sensation, in addition, there is known a feedback method to calculate a sliding speed of a user's finger and the like from a contact position on the touch sensor in order to generate a plurality of types of vibrations having vibration times differing among users corresponding to the sliding speeds (for example, see Patent Document 3).